Intraoperative physiological monitoring is a continually evolving field that aims to localize, monitor and preserve the structural and/or functional integrity of structures during surgery or other invasive procedures. For example, during spinal surgery, several neural structures may be placed at risk for potential injury (e.g., spinal cord, one or more nerve roots, lumbar plexus, vascular supply members). Generally, intraoperative physiological monitoring seeks to preserve the structural and/or functional integrity of the neural structures during surgery or other invasive procedures.
Several modalities are currently available for monitoring various aspects of the central and peripheral nervous system during surgery or other invasive procedures in order to maintain structural and/or functional integrity. Each neural monitoring modality offers a unique set of benefits and limitations as well as offering varying degrees of sensitivity or specificity. For example, the most frequently used neural monitoring modalities for spinal procedures include somatosensory evoked potentials (SSEPs), motor evoked potentials (MEPs), freerun or spontaneous EMG (sEMG), and triggered EMG (tEMG).
In lateral spine surgery, for example, the psoas muscle may be traversed by access instruments and retractors. Currently, a triggered EMG technique is used within the industry to estimate the distance of probes and instruments from nerves near the access path. Triggered EMG, however, requires a specialized suboptimal anesthesia protocol that does not paralyze the patient during the procedure. Additionally, triggered EMG does not test sensory nerves within the region of interest. Further, triggered EMG does not give information on relative health of the nerve during the procedure. As such, other modalities of intraoperative physiological monitoring are needed.